STUDY AND DESIGN OF STEP-INDEX CHANNEL WAVE-GUIDE BENDS WITH LARGE-ANGLE AND LOW-LOSS CHARACTERISTICS

By using micro-prisms, improved three-dimensional (3-D) bends of the e mbedded and buried waveguides of step-index profile are proposed, A si mple phase compensation rule for the optimal design of the micro-prism is also presented. Through the simulation of 3-D semivectorial finite -difference beam propagation method, the transmission characteristics of the improved bends are shown to have been enhanced dramatically as compared with those of the conventional ones, Even for a bend angle of as large as 10 degrees, the normalized transmitted power can still be greater than 95%, These results of 3-D bends are then compared with t hose of the two-dimensional (2-D) ones which are simplified from 3-D s tructures by the effective index method, and physical explanation of t he discrepancy between the 3-D and 2-D results is introduced, The infl uences of waveguide structures and prism parameters on the transmissio n characteristics are discussed in detail, Some criteria for the desig n of large-angle low-loss 3-D improved bends are also accessed.